R help - Aug 2010 - Does anybody know how to control the appearance of the end of the line in lattice?

Hi All,

I am plotting vertical lines using xyplot in lattice and type="h".
It works well, but the problem is that the tops of the lines are convex and the
bottoms are concave.
Is there a way to flatten the tops and bottoms?

Here's my code:

Source<-matrix(1:30,10,3)
colnames(Source)<-c("x","y1","y2")
Source<-data.frame(Source)

xyplot(y2+y1~x,
	data=Source,
	distribute.type=TRUE,
	type=c("h","h"),
	col=c("black","white"),
        lwd=20)
graphics.off()

Thanks.

George Chen

Hi

On 9/08/2010 7:49 a.m., George Chen wrote:
> Hi All,
>
> I am plotting vertical lines using xyplot in lattice and
type="h".
> It works well, but the problem is that the tops of the lines are convex and
the bottoms are concave.
> Is there a way to flatten the tops and bottoms?
You want to control the graphical parameter called "lineend", but I 
don't think this is generally made available via trellis.par.set(). 
Also, trying to set a default value via the 'grid.pars' argument, or via
a viewport with the 'draw.in' argument doesn't appear to work in
this
case (the lineend may be hard coded in the internal code somewhere). 
The following code (to be run AFTER your code) does the trick for your 
example ...

library(grid)
grid.gedit("segments", gp=gpar(lineend="butt"), grep=TRUE)

... though I believe this will also make the ends of the tick marks on 
the axes square (not obvious to the naked eye at the default size).

Paul
> Here's my code:
>
> Source<-matrix(1:30,10,3)
> colnames(Source)<-c("x","y1","y2")
> Source<-data.frame(Source)
>
> xyplot(y2+y1~x,
> 	data=Source,
> 	distribute.type=TRUE,
> 	type=c("h","h"),
> 	col=c("black","white"),
>          lwd=20)
> graphics.off()
>
> Thanks.
>
> George Chen
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
-- 
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
Auckland
New Zealand
64 9 3737599 x85392
paul at stat.auckland.ac.nz
http://www.stat.auckland.ac.nz/~paul/

On Sun, 08-Aug-2010 at 12:49PM -0700, George Chen wrote:

|> Hi All,
|>
|> I am plotting vertical lines using xyplot in lattice and
type="h".
|> It works well, but the problem is that the tops of the lines are
|> convex and the bottoms are concave.  Is there a way to flatten the
|> tops and bottoms?

The bottom isn't concave.  You've drawn a white line which has
semi-circular ends (as is the default) over the black one.

I'm having difficulty imagining what your real objective is, but if
you want to change the way the end of lines are drawn, it's simple in
base graphics using the 'lend' parameter (but it doesn't work with
all
devices according to the help file for par).

If you are using xyplot because you want to use the neat things you
can do with lattice, I think you'll have to go about it a slightly
more complicated way.  Use lpolygon in a panel function to draw
polygons and fill them.

HTH



|>
|> Here's my code:
|>
|> Source<-matrix(1:30,10,3)
|> colnames(Source)<-c("x","y1","y2")
|> Source<-data.frame(Source)
|>
|> xyplot(y2+y1~x,
|> 	data=Source,
|> 	distribute.type=TRUE,
|> 	type=c("h","h"),
|> 	col=c("black","white"),
|>         lwd=20)
|> graphics.off()
|>
|> Thanks.
|>
|> George Chen
|>
|> ______________________________________________
|> R-help at r-project.org mailing list
|> https://stat.ethz.ch/mailman/listinfo/r-help
|> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
|> and provide commented, minimal, self-contained, reproducible code.

--
Patrick Connolly
Plant & Food Research
Mt Albert
Auckland
New Zealand
Ph: +64-9 925 7079
~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~
I have the world`s largest collection of seashells. I keep it on all
the beaches of the world ... Perhaps you`ve seen it.  ---Steven Wright
~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~

On Mon, Aug 9, 2010 at 1:19 AM, George Chen <glchen at stanford.edu>
wrote:
> Hi All,
>
> I am plotting vertical lines using xyplot in lattice and
type="h".
> It works well, but the problem is that the tops of the lines are convex and
the bottoms are concave.
> Is there a way to flatten the tops and bottoms?
>
> Here's my code:
>
> Source<-matrix(1:30,10,3)
> colnames(Source)<-c("x","y1","y2")
> Source<-data.frame(Source)
>
> xyplot(y2+y1~x,
> ? ? ? ?data=Source,
> ? ? ? ?distribute.type=TRUE,
> ? ? ? ?type=c("h","h"),
> ? ? ? ?col=c("black","white"),
> ? ? ? ?lwd=20)
> graphics.off()
An additional note: If you actually want segments, then it would be
more natural to use

library(latticeExtra)
segplot(x ~ y2 + y1, data = Source, horizontal = FALSE,
        col=c("black"), lwd=20)

To get flattened corners, you could use

segplot(x ~ y2 + y1, data = Source, horizontal = FALSE,
        col=c("black"), lwd=20, lineend = "butt")

-Deepayan